Seda Yerli 20824388 Serap Sunatepe 20824245 Gonca alkan
20823894 Beytepe,Ankara12.04.2012
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OUTLINE History of IR Radiation and FTIR General Information
about IR Spectroscopy Types of IR Spectrometers Sample Preparation
Instrumentation Applications of FTIR
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Goals of presentation; To give general information about
differences between IR spectrometers about FTIR theory
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Chemical IR spectroscopy was emerged as a science in 1800 by
Sir William Herschel Firstly most IR instrumentation was based on
prism or grating monochromators Michelson invented interferometer
in 1881
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In 1949 Peter Fellgett obtained the first IR spectrum by using
FTIR spectrometer In 1960s commercial FTIR spectrometers appeared
In 1966 Cooley-Tukey developed an algorithm, which quickly does a
Fourier transform
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Spectroscopy deals with interactions between matter and energy
Figure 1 : interaction between matter and energy
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Figure 2 : electromagnetic spectrum
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Motion of atoms and molecules IR radiation higher temperature
motion more IR radiation emission
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Figure 3 : human body at normal body temperature
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Net change in molecules dipol moment Equvalence in
frequencies
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Figure 4 : vibration energy levels of molecules
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The infrared spectrum for a molecule is a graphical display The
spectrum has two regions: The fingerprint region 600-1200 cm -1
Functional group region 1200-3600 cm -1
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determining structures of compounds identifying compounds
Figure 5 : infrared spectrum of isopropanol
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Dispersive Type Fourier Transform Infrared (FTIR)
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Dispersive Type Spectrometer Having a filter or grating
monochromator Figure 6 : dispersive type spectrometer
instrumentation
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Fourier Transform Infrared Spectrometer collecting an
interferogram simultaneously measuring acquiring and digitizing the
interferogram outputing the spectrum
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Why FT-IR spectroscopy? Non-destructive technique Good
precision No external calibration High speed Signal-Noise ratio
Mechanically simple
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What information can FT-IR provide? Identify unknown material
Determine quality or consistency of sample Determine amount of
components in mixture
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Sample Preparation Gaseous samples Long pathlength to
compensate for the diluteness Liquid samples Can be sandwiched
between two plates of a salt sodium chloride potassium bromide
calcium fluoride
INSTRUMENTATION 1.Radiation Sources Black-body radiation Nernst
filament (ZrO and some other rare earth oxides) Globar (Si-C) Ni-Cr
wire Heated ceramic Mercury lamp
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2.The Interferometer spectral encoding resulting interferogram
signal obtains Figure 8 : an interferometer
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How does it work? 1.Dividing the radiation into two beams 2.One
of them goes to fixed mirror 3.Other one goes to movable mirror
4.Recombining 5.Sending to detector Figure 9: ligth travel in
interferometer
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Figure 9 : constructive-destructive interfrence of waves
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Interferogram: Name of the signal which has time domain and
occurs as a result of constructive interferences. Figure 11 : an
interferogram example
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A Fourier transform converts the time domain to the frequency
domain with absorption as a function of frequency. Figure 12:
example of spectrum that is converted by fourier transform
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3.Detectors The beam nally passes to the detector Thermal
detectors Thermocouples Bolometer Photoconducting detectors most
sensitive detectors.
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Pyroelectric detectors much faster response time insulator
material Triglycine sulphate Figure 13: pyroelectricc detector
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4.The Computer The measured signal is digitized and sent to the
computer where the Fourier transformation takes place. Figure 14 :
FTIR spectrometer
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The Sample Analysis Process Figure 15 : FTIR
spectrometeranalysis process
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Applications of FT-IR Pharmaceutical research Forensic
investigations Polymer analysis Lubricant formulation and fuel
additives Foods research Quality assurance and control
Environmental and water quality analysis methods Biochemical and
biomedical research coatings and surfactants
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References Introduction to Spectroscopy, Donald L. Pavia
Infrared Spectroscopy in Conservation Science, Michele R
Derrick,Dusan Stulik,James M. Landry
http://resources.yesicanscience.ca/trek/scisat/final/
grade9/spectrometer2.html
http://roadtickle.com/10-cool-facts-about-the- human-body
